Far Infrared (FIR; 8 to 15 μm) region is an electromagnetic wavelength band having a black body radiation intensity peak in the vicinity of the human body temperature. On the other hand, Mid Infrared (MIR; 3 to 5 μm) region, which is on the side of shorter wavelengths relative to the FIR, is an electromagnetic wavelength band having a black body radiation intensity peak at a relatively high temperature of between 200 and 400° C.
In connection with the above-described black body radiation intensity, techniques for detecting electromagnetic waves in the MIR region is used mainly for detecting high temperature objects and for detecting at the fire site, etc. On the other hand, there is a material-specific absorption peak due to rotation and vibration of molecules in the whole MIR and FIR regions. In particular, information on the molecular structure is obtained by obtaining the IR spectrum in the 2 to 20 μm band. More precisely, whether a certain functional group (alcohol, amine, ketone, aliphatic, etc.) is present can be identified; information sets on appearance of absorption in certain wavelengths may be combined to check against a database to perform material identification.
Infrared spectroscopic analysis techniques using the above-described MIR-FIR regions, including the FT-IR analysis technique, are widely used in analysis such as organic chemical analysis. FT-IR apparatuses (spectroscopy: Michelson's interferometer, detector: a cooling-type MCT, etc.), apparatuses which are superior in the precision for wavelength analysis and widely used, are analyzers for obtaining information on simple substance samples and are not for obtaining spatial distribution (camera image information). Moreover, most of the so-called infrared spectrometers (spectroscopy: a filter, etc., detector: a cooling-type MCT, etc.) are also for obtaining the information on the simple substance samples. On the other hand, while attention is focused on infrared spectropic microscopes for obtaining image information and the infrared spectrum of an image point thereof, they are quite expensive.